Spin pumping in noncollinear antiferromagnets

TL;DR

This paper provides a theoretical framework for ac spin pumping in noncollinear antiferromagnets, revealing how spin-wave modes influence spin current polarization and offering new control methods.

Contribution

It introduces a novel effective action approach to connect spin pumping and spin-transfer torque in noncollinear antiferromagnets, with specific application to kagome lattice systems.

Findings

Reactive and dissipative spin-transfer torque parameters can be extracted from the pumped spin current.

Three spin-wave bands produce orthogonal spin current polarizations.

Control of spin current orientation is possible by exciting different spin-wave modes.

Abstract

The ac spin pumping of noncollinear antiferromagnets is theoretically investigated. Starting from an effective action description of the spin system, we derive the Onsager coefficients connecting the spin pumping and spin-transfer torque associated with the dynamics of the SO(3)-valued antiferromagnetic order parameter. Our theory is applied to a kagome antiferromagnet resonantly driven by a uniform external magnetic field. We demonstrate that the reactive (dissipative) spin-transfer torque parameter can be extracted from the pumped ac spin current in-phase (in quadrature) with the driving field. Furthermore, we find that the three spin-wave bands of the kagome AF generate spin currents with mutually orthogonal polarization directions. This offers a unique way of controlling the spin orientation of the pumped spin current by exciting different spin-wave modes.